Excavation assessment on granitic area at Ulu Kinta, Perak, Malaysia for an earthwork project

Surface excavation work in tropically weathered rocks is challenging due to many uncertainties such as rock mass and material properties, environment, selection of best excavation method, machine characteristics, cost and production rate. The weathering profile of rock mass in the tropical region can be variable, unpredictable, and dominant in controlling rock behavior. Issues in confirmation on hard mass and rock mass in the surface excavation are discussed in this paper mainly in terms of definition and its relation to Jabatan Kerja Raya (JKR) Standard Specification Sect. 2:Earthwork, as essential references for practitioners related to surface excavation. It is crucial to ensure a reliable assessment on the most critical factors to reduce costs and unnecessary time delays. The study area is Ulu Kinta, Perak which is underlaid by granitic. This site was selected for this study because of the ongoing earthworks and exposure to rock outcrops. This study involved two geophysical methods, namely the 2D-Resistivity Method and Seismic velocity. Geophysical methods are beneficial for determining bedrock, type, and estimation of the volume of rock to be excavated for the areas, especially in the early stages of earthwork. The condition of the site consists of various grades where Grade I and Grade II granite was found at a depth of 33 m from the ground surface. Based on the correlation between borehole and seismic refraction, the overburden layer is dominated by low velocity values (<800 m/s) that correspond to low N values. This study also investigated the effect of moisture content on various grades of weathered granites, focusing on strength. It was found that moisture significantly affects weaker materials such as Grade IV and V was than stronger materials (Grade I and II). The trial excavation is carried out based on one type of excavator (EX 300), thus, confirmation can only be made to determine the hard mass for this area. The drilling method correlated well with the borehole result and proposed an alternative method in determining the hard and rock mass. Rock mass properties should be considered in the assessment, play a significant role in influenced excavatability and avoid problems that arise during excavation work

Fracture characterization using downhole camera in deep boreholes at Southern Johor Bahru, Malaysia

Downhole camera is an effective tool to locate fractures and other geological features in boreholes although it does not quantify the characteristics of fracture directly. This study attempts to qualitatively characterize fractures in three deep boreholes, namely W1-W3 using downhole camera of R-CAM 1000 XLT as well as to investigate the geological features present at Southern Johor Bahru. The study area is underlain by Jurong Formation and Older Alluvium. Jurong Formation comprises of well cemented and consolidated volcanic-sedimentary rocks while Older Alluvium comprises of coarse, angular clayey sand with pebbles such as quartz, rhyolite, chert and argillite pebbles. The geological features encountered during the study are brecciated zone and veins such as quartz, calcite and pyrite. In addition, the fracture density in W2 (175/150 m) is found to be higher than W1 (79/165 m). Gently dipped (<20°), single set of joints with tight to open aperture (<0.1–4 cm) are dominant in both wells. Major orientation of discontinuities is north-east (0–90°) to south-west (180–270°) which is subparallel to bedding plane and lineament orientations. Meanwhile, no major structure is observed in W3. Thus, the study shows the importance of downhole camera survey in locating and characterizing fractures in rock mass qualitatively